Subsea flowline connections have been made by telescoping connections as shown in the R. L. Geer et al U.S. Pat. Nos. 3,052,299 and 3,233,666. Such structures rely on sealing rings for sealing of the telescoping joint. Such seals do not have the durability of metal-to-metal seals, are not either remotely actuated or actuated and are not latched in sealing position independent of the actuation of the telescoping movement.
Another example of an extensible flowline connector which is remotely actuated is shown in the J. H. Fowler U.S. Pat. No. 3,732,923 but such patent does not have a remotely and separately actuated metal-to-metal seal. Stems on valves have been protected by bellows type of extensible members as shown in the J. Kosik U.S. Pat. No. 3,128,078.
It is advantageous if the subsea wellhead may be separately installed, disconnected and recovered without disturbing the subsea flowlines.